Rollable knife sharpener

Abstract

Knife sharpener rollable on a support and having two substantially coaxially disposed equally sized rollers (2,4) pressed resiliently against each other. The rollers have on their facing sides externally conical intermeshing toothed rings (32) which consist at least at their facing faces (38) of a durable grinding material. The knife blade to be sharpened is introduced between the two toothed rings, the latter being pressed apart in the respective region. The grinding action is effected by the relative movement of the end faces of the toothed rings with respect to the blade drawn or pushed through, while the knife sharpener rolls on the support.

I claim: 
     
       1. A rollable knife sharpener in which the grinding takes place in a direction which is predominantly normal to the cutting edge of the knife, said rollable knife sharpener comprising: (a) a first roller which is symmetrical about a rolling axis and which has an inside axial surface and an outside axial surface, said first roller having a threaded axial bore extending from its inside axial surface part way therethrough and a first blind bore which is larger in diameter than said threaded bore, which is coaxial with said threaded bore, and which extends from said threaded bore to the outside axial surface of said first roller;   (b) a second roller which is symmetrical about a rolling axis which is coincident with the rolling axis of said first roller, said second roller having the same radial dimensions as said first roller, said second roller having an inside axial surface facing the inside axial surface of said first roller and an outside axial surface, said second roller having a cylindrical axial bore which is larger in diameter than said threaded axial bore in said first roller and which extends from the inside surface of said second roller part way through said second roller and a second blind bore which is larger in diameter than said cylindrical axial bore, which is coaxial with said threaded axial bore, and which extends from said cylindrical axial bore to the outside axial surface of said second roller;   (c) a shaft comprising a threaded first portion threadably received in said threaded axial bore, an unthreaded second portion received in said cylindrical axial bore and said second blind bore, and a head which bears against the outside axial surface of said second roller, the threaded engagement between said threaded first portion of said shaft and said threaded axial bore and the contact of said head with the outside axial surface of said second roller limiting relative axial movement of said first and second rollers, said unthreaded second portion of said shaft being smaller in diameter than said cylindrical axial bore, thereby permitting tilting movement between said shaft and said second roller;   (d) a plug cap closing the axially outer end of said first blind bore;   (e) two substantially coaxially disposed, equally sized toothed rings disposed coaxially between said first and second rollers, one of said toothed rings being mounted on the inner axial surface of said first roller and the outer one of said toothed rings being mounted on the inner axial surface of said second roller, each of said two toothed rings having a large number of generally axially projecting teeth which are sized, shaped, and positioned to intermesh with the teeth on the other one of said two toothed rings, the radially outer peripheries of the teeth on said toothed rings forming a V-shaped gap sized and shaped to receive a knife blade to be sharpened by the rolling movement of said first and second rollers, at least the working surface of the V-shaped gap being formed of a grinding material; and   (f) a compression spring disposed in said second blind bore and bearing again said head of said shaft and said second roller, said compression spring serving to bias said two toothed rings resiliently towards each other, whereby:     (g) when the sharpener is placed on a planar support and a knife blade is introduced into the V-shaped gap between said two toothed rings, said first and second rollers tilt slightly relative to each other and are forced somewhat apart against the resilient force of said compression spring and the knife blade is firmly gripped between said two toothed rings, and   (h) when said first and second rollers are rolled on the planar support, said teeth are caused to grind the knife blade in a direction which is predominantly normal to the cutting edge of the knife blade, thereby cutting minute gouges on each side of the knife blade in the direction perpendicular to its edge.   
     
     
       2. Knife sharpener according to claim 1, characterized in that each of the two toothed rings has between 15 and 60 teeth. 
     
     
       3. Knife sharpener according to claim 2, characterized in that each of the two toothed rings has 25 teeth. 
     
     
       4. Knife sharpener according to claim 2, characterized in that the two toothed rings are formed of a ceramic grinding material. 
     
     
       5. Knife sharpener according to claim 4, characterized in that the two toothed rings are formed of a ceramic grinding material containing a grinding compound selected from the group consisting of aluminum oxide and silicon carbide. 
     
     
       6. Knife sharpener according to claim 2, characterized in that the two toothed rings are formed of metal coated with a grinding material. 
     
     
       7. Knife sharpener according to claim 6, characterized in that the coating of grinding material comprises a layer having the composition 10 to 30% tungsten carbide, 20 to 50% silicon carbide, and 30 to 50% a ceramic binder. 
     
     
       8. Knife sharpener according to claim 7 characterized in that the coating of grinding material comprises a layer having a composition of about 20% tungsten carbide, about 40% silicon carbide, and about 40% of a ceramic binder, to which a hard chromium layer has been applied. 
     
     
       9. Knife sharpener according to claim 1, characterized in that each of the two rollers is made of plastic and has at its periphery a friction covering. 
     
     
       10. Knife sharpener according to claim 9 wherein the friction covering is formed of rubber. 
     
     
       11. A rollable knife sharpener as recited in claim 1: (a) wherein said threaded shaft extends into said first blind bore and   (b) further comprising a nut threaded onto said threaded shaft and bearing against said first roller.   
     
     
       12. A rollabale knife sharpener as recited in claim 1 wherein: (a) said first blind bore has a first annular widening at the outside axial surface of said first roller and   (b) said plug cap is received in said first annular widening.   
     
     
       13. A rollable knife sharpener as recited in claim 1 wherein: (a) said second blind bore has a second annular widening at the outside axial surface of said second roller and   (b) said head is received in said second annular widening.   
     
     
       14. A rollable knife sharpener as recited in claim 1 wherein: (a) a first shallow groove is formed in the periphery of said first roller and   (b) a second shallow groove is formed in the periphery of said second roller and further comprising   (c) a first rectangularly profiled rubber band inserted into said first shallow groove as friction covering and   (d) a second rectangularly profiled rubber band inserted into said second shallow groove as friction covering.   
     
     
       15. A rollable knife sharpener as recited in claim 1 wherein the profile of said teeth are slightly curved in the radial direction. 
     
     
       16. A rollable knife sharpener in which the grinding takes place in a direction which is predominantly normal to the cutting edge of the knife, said rollable knife sharpener comprising: (a) a first roller which is symmetrical about a rolling axis and which has an inside axial surface and an outside axial surface, said first roller having a first axial bore extending from its inside axial surface part way therethrough and a first blind bore which is larger in diameter than said first axial bore, which is coaxial with said first axial bore, and which extends from said first axial bore to the outside axial surface of said first roller;   (b) a second roller which is symmetrical about a rolling axis which is coincident with the rolling axis of said first roller, said second roller having the same radial dimensions as said first roller, said second roller having an inside axial surface facing the inside axial surface of said first roller and an outside axial surface, said second roller having a second axial bore extending from its inside axial surface part way therethrough and a second blind bore which is larger in diameter than said second axial bore, which is coaxial with said second axial bore, and which extends from said second axial bore to the outside axial surface of said second roller;   (c) a shaft comprising a threaded first portion received in said first blind bore, a second portion received in said first and second axial bores, and a head which bears against the outside axial surface of said second roller, said second portion of said shaft being smaller in diameter than at least one of said first and second axial bores, thereby permitting tilting movement between said shaft and at least one of said roller;   (d) a plug cap closing the axially outer end of said first blind bore;   (e) a nut threaded onto said threaded first portion of said shaft and bearing against said first roller, the threaded engagement between said threaded first portion of said shaft and said nut and the contact of said head with the outside axial surface of said second roller limiting relative axial movement of said first and second rollers;   (f) two substantially coaxially disposed, equally sized toothed rings disposed coaxially between said first and second rollers, one of said toothed rings being mounted on the inner axial surface of said first roller and the other one of said toothed rings being mounted on the inner axial surface of said second roller, each of said toothed rings having a large number of generally axially projecting teeth which are sized, shaped, and positioned to intermesh with the teeth on the other one of said toothed rings, the radially outer peripheries of the teeth on said toothed rings forming a V-shaped gap sized and shaped to receive a knife blade to be sharpened by the rolling movement of said first and second rollers, at least the working surface of the V-shaped gap being formed of a grinding material; and   (g) a compression spring disposed in said second blind bore and bearing against said head of said shaft and said second roller, said compression spring serving to bias said toothed rings resiliently towards each other, whereby:     (h) when the sharpener is placed on a planar support and a knife blade is introduced into the V-shaped gap between said toothed rings, said rollers tilt slightly relative to each other and are forced somewhat apart against the resilient force of said compression spring and the knife blade is firmly gripped between said toothed rings, and   (i) when said first and second rollers are rolled on the planar support, said teeth are caused to grind the knife blade in a direction which is predominantly normal to the cutting edge of the knife blade, thereby cutting minute gouges on each side of the knife blade in the direction perpendicular to its edge.   
     
     
       17. A rollable knife sharpener as recited in claim 16 wherein: (a) said first blind bore has a first annular widening at the outside axial surface of said first roller;   (b) said plug cap is received in said first annular widening;   (c) said second blind bore has a second annular widening at the outside axial surface of said second roller; and   (d) said head of said shaft is received in said second annular widening.   
     
     
       18. A rollable knife sharpener as recited in claim 16 wherein: (a) a first shallow groove is formed in the periphery of said first roller and   (b) a second shallow groove is formed in the periphery of said second roller and further comprising:     (c) a first rectangularly profiled rubber band inserted into said first shallow groove as friction covering; and   (d) a second rectangularly profiled rubber band inserted into said second shallow groove as friction covering.   
     
     
       19. A rollable knife sharpener as recited in claim 16 wherein the profile of said teeth are slightly curved in the radial direction. 
     
     
       20. A rollable knife sharptener as recited in claim 16 wherein said second portion of said shaft is smaller in diameter than said second axial bore, thereby permitting tilting movement between said shaft and said second roller.